1. Field of the Invention
The present invention generally relates to a die casting machine and a die therefor, and particularly, it relates to a die casting machine with a pressure supervisory system for supervising a set of pressures including a pressure of a body of atmosphere in a die cavity (hereafter sometimes "cavity pressure") to produce a casting with an upgraded quality, and a die therefor.
2. Description of Relevant Art
The die casting machine employs a set of two or more dies as casting molds therefor that have a cavity defined therebetween when locked or clamped together.
Gases in the die cavity should be vented, when injecting molten metal. For a casting with a stable quality, it is important to surely vent the gases. The die cavity has one or more gas vents, which may occasionally fail to sufficiently vent gases containing e.g. gasified die lubricant, because of a body of lubricant accumulated or deformed with heat or by intensified locking forces, or the like.
An insufficient venting of such gases raises the cavity pressure. While a body of gases as atmosphere left in the die cavity has an increased pressure, a required pressure for casting a body of injected molten metal has a fraction thereof absorbed by the residual atmosphere so that the molten metal has an insufficient pressure acting thereon, occasionally receiving additional adverse influences such as by parts of the atmosphere entangled in the molten metal, resulting in an increased ratio of non-conforming products with a problem in quality.
Conventionally, there has been detected a flow rate of gases discharged from a gas vent, to externally check a state of atmosphere in a die cavity, when molten metal is injected thereto. A flow sensor is installed outside dies to measure a flow rate of gas streams in a secondary passage making use an effect of an ejector. A long service life of the flow sensor is thus expectable.
However, such the conventional measurement is subject to a reduced accuracy due such as to a blocking of a diffuser due to a flushing and an influence of dust in atmosphere around the sensor.
Further, as a die cavity has a number of gas vents, it is necessary for an effective quality control of castings to provide an identical number of gas flow meters for measuring gas flow rates of the gas vents, thus needing an impractical complicated system.